According to DxOMark, the Sigma 24-35mm f/2 DG HSM Art is an excellent performer. It has good consistent sharpness at f/2 throughout the range, but stopping down improves both sharpness and uniformity, particularly at the shorter end.

Sigma 24-35mm f/2 DG HSM Art Lens for Canon Mount Gets DxOMarked

“At around $999, the Sigma 24-35mm f2 DG HSM A is certainly an intriguing option for Canon users. Image quality challenges Canon’s 24mm f2.8 IS and 35mm f2.0 IS primes once stopped down, and saves around $200 in the bargain. With the 28mm f2.8 IS at around $569, there’s even more tempting savings to be had. Optical quality like this costs money. The Canon models have stabilization, which is difficult to put on a price on, but others might be more attracted by the zoom’s flexibility: changing lenses is a chore at best and is especially so in hazardous environments.

Sigma has done well to introduce this model, but it is so good that it’s in danger of competing with the company’s own high-speed f/1.4 models. However, while they stand out for their quality at wider apertures, this new zoom is rather the more practical and arguably more useful option for everyday shooting.”

Sigma 24-35mm f/2 DG HSM Art Lens is the market’s first full-frame zoom that allows photographers to carry one fast aperture lens that can do the work of three popular fixed focal length lenses – the 24mm, 28mm and 35mm. The lens has a minimum focusing distance of 28cm, giving a maximum magnification ratio of 1:4.4. See sample images here.